Method and system for measuring an object in digital image

ABSTRACT

A method and a system of measuring an object in a two-dimensional digital image are provided. The object is moved to cover the portion that is outside a viewing window, and a first image of the object, which is captured before the object is moved, and a second image of the object, which is captured after the object is moved are used in measuring. Displacement of the image is detected by comparing the position of one reference point of the object in the first image and the position of the same reference point of the object in the second image. And the geometrical data of the object is calculated with the displacement data. The second image is overlapped with the first image by finding the position at which sum of the luminosity value of the first image and the reversed luminosity value of the second image is minimized.

BACKGROUND OF THE INVENTION

The present invention relates to method and system of measuring anobject in a digital image. More particularly, this invention relates tomethod and system of measuring an object in a digital image when theimage is bigger than a viewing window of an optical instrument such as amicroscope.

There have been many image analysis programs or image measurementprograms that measure objects in a digital image obtained by amicroscope or a digital camera with the pixel values displayed in acomputer monitor window that is connected to the microscope or digitalcamera. If an object is big and thus cannot be displayed as a whole inthe monitor window, direct measurement from the image displayed in themonitor at a given moment is not possible.

In order to measure such oversize objects, a measuring microscope with ameasuring stage and a profile projector have been used. FIG. 1 shows anexample of a microscope 10 by prior art. A measuring stage 12 moves anobject in X/Y/Z axes, and provides the X/Y/Z coordinates of an objectbefore and after the movement. A measuring program by prior art used thedata provided by a measuring stage to measure the size of an object in adigital image. A measuring stage needs to provide precise movement of anobject to be measured and accurately measure movement in the XY plane orthe XYZ space. This requires expensive mechanical parts, interfaces andother accommodations between the measuring stage and the measuringprogram.

SUMMARY OF THE INVENTION

The present invention contrives to solve the disadvantages of the priorart.

An objective of the invention is to provide a measuring method andsystem for measuring oversize objects in a digital image without ameasuring stage.

Another objective of the invention is to provide a digital imagemeasuring method and system that has a manual, semi-automatic andautomatic modes to maximize efficiency and versatility of the system.

Still another objective of the invention is to provide a digital imagemeasuring method and system that can recognize and determine the movingdistance and geometrical data of multiple objects in a digital image.

To achieve the above objectives, the present invention provides a methodof measuring an object in a two-dimensional digital image. The object ismoved to cover a portion of the object that is not viewed in a viewingwindow. A first image of the object, which is captured before the objectis moved, and a second image of the object, which is captured after theobject is moved, are used in measuring. The method includes the steps ofdetecting two-dimensional displacement of the image by comparing theposition of one reference point of the object in the first image and theposition of the same reference point of the object in the second image,and calculating geometrical data of the object.

The step of detecting two-dimensional displacement includes moving thesecond image so that the second image overlaps the first image.

In the step of moving the second image, overlapping is determined byminimizing sum of the luminosity value of a specific point or area ofthe first image and the luminosity value of the same point or area ofthe second image. The luminosity of a part of the second image, whichincludes the point or area, is set to be the negative value of theluminosity of the originally captured second image.

The step of detecting two-dimensional displacement may be repeated oneor more times in order to cover a large object.

In the step of detecting two-dimensional displacement, the coordinatesof one or more points of the object in the first image are memorized.When the object is moved, the displacement of the object isautomatically calculated. The automatic calculation may be performedwithin a partial range of the first image determined by a user. This isadvantageous when there are many objects of the same pattern. Theoverlapping may be performed manually also.

In case that the geometrical data is one-dimensional, thetwo-dimensional coordinates of a measuring point of the first imagerelative to the reference point, and the two-dimensional coordinates ofa measuring point of the second image relative to the reference pointare used in the step of calculating the geometrical data of the object.

In case that the geometrical data is two-dimensional, thetwo-dimensional coordinates of one or more measuring points of the firstimage relative to the reference point, and the two-dimensionalcoordinates of one or more measuring points of the second image relativeto the reference point are used in the step of calculating thegeometrical data of the object.

The invention also provides a system of measuring an object in atwo-dimensional digital image. The system includes a detection moduledetecting two-dimensional displacement of the image by comparing theposition of one reference point of the object in the first image and theposition of the same reference point of the object in the second image,and a calculation module calculating geometrical data of the object.

The detection module moves the second image so that the second imageoverlaps the first image. In the detection module, overlapping isdetermined by minimizing sum of the luminosity value of a specific pointor area of the first image and the luminosity value of the same point orarea of the second image. The luminosity of a part of the second image,which includes the point or area, is set to be the negative value of theluminosity of the originally captured second image.

The detection module repeats detecting two-dimensional displacement oneor more times as needed.

The detection module memorizes the coordinates of one or more points ofthe object in the first image. When the object is moved, the detectionmodule automatically calculates the displacement of the object. Thiscalculation may be performed within a partial range of the first imagedetermined by a user.

The calculation module uses the two-dimensional coordinates of one ormore measuring points of the first image relative to the referencepoint, and the two-dimensional coordinates of one or more measuringpoints of the second image relative to the reference point incalculating the one-dimensional or two-dimensional geometrical data ofthe object.

The advantages of the present invention are: (1) a digital microscopethat does not need a measuring stage and measures objects only from thedata included in digital images themselves is provided; and (2) adigital image measuring software that has various user-friendly featuresand powerful calculation options is provided.

Although the present invention is briefly summarized, the fullerunderstanding of the invention can be obtained by the followingdrawings, detailed description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention will become better understood with reference to theaccompanying drawings, wherein:

FIG. 1 is a schematic elevation view showing a microscope by prior art;

FIG. 2 is a flow diagram showing a digital image measuring methodaccording to the present invention;

FIG. 3 is a block diagram showing a digital image measuring systemaccording to the present invention;

FIG. 4 is a screen capture showing a preview window;

FIG. 5 is a screen capture showing a reference point on a object in afirst image;

FIG. 6 is a screen capture showing a second image of the moved object;

FIG. 7 is a screen capture showing the first image and the second imagesimultaneously;

FIG. 8 is a screen capture showing the second image is overlapped withthe first image;

FIG. 9 is a screen capture showing coordinates of the reference point iscompensated;

FIG. 10 is a screen capture showing coordinates of a point on the objectis compensated; and

FIG. 11 is a screen capture showing a menu for automatic calculationparameters.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 2 shows a flow diagram for a digital image measuring methodaccording to the present invention. The object is moved to cover aportion of the object that is not viewed in a viewing window 14 (referto FIG. 4). A first image 16 of the object (refer to FIG. 5), which iscaptured before the object is moved, and a second image 18 of the object(refer to FIG. 6), which is captured after the object is moved are usedin measuring. The method includes step S01 of detecting two-dimensionaldisplacement of the image by comparing the position of one referencepoint of the object in the first image and the position of the samereference point of the object in the second image, and step S02 ofcalculating geometrical data of the object.

FIG. 3 shows a digital image measuring system 20 according to thepresent invention. The system 20 includes a detection module 22 thatdetects two-dimensional displacement of the image by comparing theposition of one reference point 24 (refer to FIG. 5) of the object inthe first image 16 and the position of the same reference point 24 ofthe object in the second image 18, and a calculation module 26 thatcalculates geometrical data of the object.

FIGS. 4-10 are screen captures that illustrate operations of the system20. FIG. 4 shows the viewing window 14 of a digital optical instrument,for example, a microscope. FIG. 5 shows a reference point 24 on anobject 28 in the first image 16.

The object 28 is moved in order to cover portions of the object 28 thatare not seen in the viewing window 14. This movement is done by a stageattached to a microscope. In this case the stage has only the role ofmoving the object 28 and does not provide displacement data like ameasuring stage. The first image 16 is captured before the object 28 ismoved, and the second image 18 is captured after the object 28 is moved.FIG. 6 shows the second image 18 of the moved object 28 with a referencepoint 24′ that corresponds the reference point 24 of the first image 16.FIG. 7 shows the first image 16 and the second image 18 simultaneously.

Step S01 of detecting two-dimensional displacement S01 includes a stepS03 of moving the second image 18 or the first image 16 so that thesecond image 18 overlaps the first image 16. This movement of the secondimage 18 is performed by the detection module 22 of the digital imagemeasuring system 20.

FIG. 8 shows that the second image 18 is overlapped with the first image16 with the reference point 24, 24′ coincided with each other.

In step S03 of moving the second image, overlapping is determined byminimizing sum of the luminosity value of the reference point 24 or anarea of the first image 16 and the luminosity value of the referencepoint 24′ or an area of the second image 18. The luminosity of a part ofthe second image 18, which includes the reference point 24′ or area, isset to be the negative value of the luminosity of the originallycaptured second image 18.

Step S01 of detecting two-dimensional displacement may be repeated oneor more times by the detection module 22 in order to cover a largeobject.

In a first embodiment, in step S01 of detecting two-dimensionaldisplacement, the coordinates of one or more points of the object 28 inthe first image 16 are memorized by the detection module 22. When theobject 28 is moved, the displacement of the object 28 is automaticallycalculated by the detection module 22.

In a second embodiment, the automatic calculation may be performedwithin a partial range of the first image 16 determined by a user. Thefirst image 16 or the second image 18 is moved to the other imagemanually. Then automatic detection is perform with the partial range.This is advantageous when there are many objects of the same pattern. Ina third embodiment, the overlapping is performed by manually moving theobject 28. An indicator shows the sum of luminosity values that isexplained above. When the value shown by the indicator is minimized, thefirst image 16 and the second image 18 are overlapped.

In case that the geometrical data is one-dimensional, such as length orwidth of the object 28, the two-dimensional coordinates of a measuringpoint of the first image 16 relative to the reference point 24, and thetwo-dimensional coordinates of a measuring point of the second image 18relative to the reference point 24′ are used in step S02 of calculatingthe geometrical data of the object 28 by the calculation 26 of thedigital image measuring system 20.

In case that the geometrical data is two-dimensional, such as the areaof the object 28, the two-dimensional coordinates of one or moremeasuring points of the first image 16 relative to the reference point24, and the two-dimensional coordinates of one or more measuring pointsof the second image 18 relative to the reference point 24′ are used instep S02 of calculating the geometrical data of the object 28.

The geometrical data provided by the digital image measuring system 20includes the length, area, radius, diameter, angle and distance, etc. ofthe object 28.

FIG. 9 shows that coordinates of the reference point 24, 24′ iscompensated or calculated according to the result of step S01. Arrow 1means X, Y coordinate pixel values of the moved window. Arrow 2 showsthat X, Y coordinates of the reference points are compensated with thevalue indicated by arrow 1.

FIG. 10 shows that the coordinates of a point 30 on the object 28 iscompensated or calculated in a way similar to that in FIG. 9.

FIG. 11 shows a menu for automatic calculation parameters that are usedin the method of the present invention. Max movement scan indicates therange in which the digital image measuring system 20 detectsdisplacements automatically. Primary direction means X-axis, andsecondary direction means Y-axis. FIG. 11 shows the range as 500 pixelsin primary direction and 70 pixels in the secondary direction. Thenumbers can be adjusted by the user.

While the invention has been shown and described with reference todifferent embodiments thereof, it will be appreciated by those skilledin the art that variations in form, detail, compositions and operationmay be made without departing from the spirit and scope of the inventionas defined by the accompanying claims.

1. A method of measuring an object in a two-dimensional digital image,wherein the object is moved, and a first image of the object, which iscaptured before the object is moved, and a second image of the object,which is captured after the object is moved are used in measuring, themethod comprising: a) detecting two-dimensional displacement of theimage by comparing the position of one reference point of the object inthe first image and the position of the same reference point of theobject in the second image; and b) calculating geometrical data of theobject.
 2. The method of claim 1, wherein the step of detectingtwo-dimensional displacement comprises moving the second image so thatthe second image overlaps the first image.
 3. The method of claim 2,wherein in the step of moving the second image, overlapping isdetermined by minimizing sum of the luminosity value of a specific pointor area of the first image and the luminosity value of the same point orarea of the second image, wherein the luminosity of a part of the secondimage, which includes the point or area, is set to be the negative valueof the luminosity of the originally captured second image.
 4. The methodof claim 2, wherein the step of detecting two-dimensional displacementis repeated one or more times.
 5. The method of claim 2, wherein in thestep of detecting two-dimensional displacement, the coordinates of oneor more points of the object in the first image are memorized, whereinwhen the object is moved, the displacement of the object isautomatically calculated.
 6. The method of claim 2, wherein in the stepof detecting two-dimensional displacement, the coordinates of one ormore points of the object in the first image are memorized, wherein whenthe object is moved, the displacement of the object is automaticallycalculated within a partial range of the first image determined by auser.
 7. The method of claim 2, wherein the geometrical data isone-dimensional, wherein the two-dimensional coordinates of a measuringpoint of the first image relative to the reference point, and thetwo-dimensional coordinates of a measuring point of the second imagerelative to the reference point are used in the step of calculating thegeometrical data of the object.
 8. The method of claim 2, wherein thegeometrical data is two-dimensional, wherein the two-dimensionalcoordinates of one or more measuring points of the first image relativeto the reference point, and the two-dimensional coordinates of one ormore measuring points of the second image relative to the referencepoint are used in the step of calculating the geometrical data of theobject.
 9. A system of measuring an object in a two-dimensional digitalimage, wherein the object is moved, and a first image of the object,which is captured before the object is moved, and a second image of theobject, which is captured after the object is moved are used inmeasuring, the system comprising: a) a detection module detectingtwo-dimensional displacement of the image by comparing the position ofone reference point of the object in the first image and the position ofthe same reference point of the object in the second image; and b) acalculation module calculating geometrical data of the object.
 10. Thesystem of claim 9, wherein the detection module moves the second imageso that the second image overlaps the first image.
 11. The system ofclaim 10, wherein in the detection module, overlapping is determined byminimizing sum of the luminosity value of a specific point or area ofthe first image and the luminosity value of the same point or area ofthe second image, wherein the luminosity of a part of the second image,which includes the point or area, is set to be the negative value of theluminosity of the originally captured second image.
 12. The system ofclaim 10, wherein the detection module repeats detecting two-dimensionaldisplacement one or more times.
 13. The system of claim 10, wherein thedetection module memorizes the coordinates of one or more points of theobject in the first image, wherein when the object is moved, thedetection module automatically calculates the displacement of theobject.
 14. The system of claim 10, wherein the detection modulememorizes the coordinates of one or more points of the object in thefirst image, wherein when the object is moved, the detection moduleautomatically calculates the displacement of the object within a partialrange of the first image determined by a user.
 15. The system of claim10, wherein the geometrical data is one-dimensional, wherein thetwo-dimensional coordinates of a measuring point of the first imagerelative to the reference point, and the two-dimensional coordinates ofa measuring point of the second image relative to the reference pointare used by the calculation module in calculating the geometrical dataof the object.
 16. The system of claim 10, wherein the geometrical datais two-dimensional, wherein the two-dimensional coordinates of one ormore measuring points of the first image relative to the referencepoint, and the two-dimensional coordinates of one or more measuringpoints of the second image relative to the reference point are used bythe calculation module in calculating the geometrical data of theobject.